Carburetors



i 1: Fri g May 28, 1957 FIG 0 R E i 21--+ 7b ENG/NE J COOL ANT #54 7'Elam/V656 FIGURE 5 M. B. HEFTLER ETAL ENG/NE FIGURE 2 I N VEN TORfSUnited States Patent Office CARBURETORS Maurice Ben Heftler and PierreVictor Heftler, Grosse Pointe Park, Mich.

Application May'24, 1952, Serial No. 289,755 6 Claims. (Cl. 1 23-122)This invention provides inexpensive and simple means to feed arelatively rich fuel air mixture to spark ignition gasoline enginesduring the warming up period and to lean out this rich mixture to theproper running ratio as the engine warms up to normal operatingtemperature. It is particularly effective at low speeds and light loads,where it is most needed;

This invention solves the problem of supplying a rich mixture to a coldengine in a new way. Instead of restricting the air intake, When theengine is cold, which is the conventional method, this inventionoperates on theidle fuel channel and restricts the fuel delivered whenthe engine is warm. It modifies the normal action of the conventionalidle by-pass circuit by adding a heat responsive element arranged sothat the quantity, or richness, or both, of the mixture'delivered bythefldle bypass is decreased by an increase in temperature. By operatingon the fuel instead of the air intake several advantages result.First,-the cost is small. Secondly, there are a variety of methods foreasily making the cold engine enrichment automatically responsive totemperature, and some of them require no moving parts. Lastly, by takingadvantage of the fact that the idle system, or low speed circuit, of thecarburetor, which supplies all of the fuel at idle, becomes ofdecreasing importance as the throttle is opened, it is possible toprovide cold engine enrichment at low speeds where it is most needed,and automatically taper off the enrichmerit as the speed increases.

The drawings schematically show the invention applied to a carburetor,in three different forms, as follows:

In Figure 1 the idle enrichment is reduced by opening an additional airbleed into the idle by-pass circuit in response to increase intemperature. In Figure 2 the idle enrichment is decreased by heating theair-fuel emulsion in the idle by-pass circuit. In Figure 3, anadaptation of Figure 2, the idle by-pass circuit divides into twobranches and the fuel emulsion in one branch is heated. For simplicity,the drawings are somewhat schematic and show the invention applied to aconventional, single bore, downdraft carburetor.

Referring to Figure 1, the discharge nozzle 1 draws fuel from below theliquid level LL and discharges it into the throat of the venturi 2. Theair flow is controlled by the throttle plate 3, here shown in a lowspeed position, under which condition fuel is being delivered by theidle by-pass system.

The engine induction vacuum existing in the manifold 4 is applied to thepriming holes 5 to draw an emulsion of fuel and air from the idleby'pass circuit. The idle by-pass circuit consists of idle channels 6,7, 8 and 9 leading up from the holes 5 and down to the liquid level LL.Associated with these idle channels there is shown, as found in manycarburetors, a restriction 10 located at or near the fuel level LL, anair bleed 11, and an adjustable air bleed or an adjustment screw on thelower priming hole. All that has been so far described is conventional,although the particular arrangement of restrictions and of fixed andmanually adjusted air-bleeds in the idle by-pass circuit may vary withdifferent makes of carburetors. t

Figure 1 differs from the conventional carburetor in that the idlebypass circuit has an additional specially controlled air-bleed. Arestricted air vent 14 admits air.

When the thermostat 16 is cold the valve 15 is closed and,

the mixture delivered by the idle by-pass system out of priming holes 5is quite rich, as required by a cold engine.

As the engine warms up, thermostat 16 gets Warm and gradually opensvalve 15 thus admitting air into channel 7 and leaning out the mixturedelivered by priminghole 5. The restricted air vent 14 may be small inrelation to the valve 15, so that only the first part of the valvetravel is effective in leaning out the mixture, or it may be very largeso that equal increments of valve travel are about equally effective inadmitting additional air. The choice in design will hinge on the sourceof heat supplied to the thermostat, and on how rapidly and to what levelit getsgwarm compared to the diminishing demand for fuel as the enginewarms up. 7

Referring now to Figure 2, we show a second form of the invention. Againthere is shown the main jet 1,

ventu ri 2, throttle 3, manifold 4, the priming holes 5 and the idleby-pass circuit leading from the liquid level LL to the holes 5.However, in 7a, the mid-portion of the idle by-pass circuit, there is aheat exchanger 18 through which the fuel-air emulsion of the idle systemmust flow before it reaches channel 6 and the priming holes 5.

The heat exchanger 18 is heated by the engine or by some part or mediumassociated with the engine. It can be built into a cylinder head bolt,and on liquid cooled engines its maximum temperature" can be'limited bythe coolant thermostat. When the engine is cold the mixture of fuel andair passes through 18 tothe'primin'gwholes 5 substantially unchanged. Asthe engine warms up, this mixture is expanded in the heat exchanger 18,and when the temperature of the heat exchanger reaches the vaporizationtemperature of the fuel the expansion becomes very pronounced. When thefuel is alcohol, with a single boiling point, the expansion is veryrapid at about F. With gasoline the expansion is spread over aconsiderable temperature range, because of the boiling characteristicsof the fuel.

The amount, by weight, of the fuel-air mixture aspirated into the engineby the suction at priming holes 5 decreases as the mixture is expandedby heat. Thus, when the engine is cold, it is supplied with more fuelthan when it is hot.

Referring now to Figure 3, we show a. third form of the inventionsomewhat similar to Figure 2. Here, the idle by-pass circuit is divided,for part of its length, into two parallel channels 7a and 7b. Channel 7agoes through a heat exchanger 18, as in the case of Figure 2, butchannel 7b has no heat exchanger. These two parallel circuits, 7a and715, may be controlled by suitable restrictions 19, 20 and 21 so as todivide the fuel-air mixture between them in the best way.

The point of having parallel circuits is this: It may be desirable toheat the heat exchanger 18 by a medium that has a very broad swing intemperature as the engine warms up from a cold start to normal operatingtemperature, such as the exhaust manifold. In that case Patented May 28,1957- the expansion-of the fuel due to the heat may be more than isrequired. The unheated parallel channel 7b provides a means of limitingthe effect of this excess expansion, and restrictions 19, 20, and 21provide means of-utilizing exactly that amount of the expansion thatbest meets the needs of the engine. I

We claim:

1. Ina carburetor for an internal combustion engine with a throttle inthe mainair stream and a constant level fuel bowl, a low speed throttleby-pass circuit including a fuel restriction to a channel leading to apoint above the fuel level in said bowl, an air admission port to saidchannel, a discharge port from said channel to said main air stream at apoint between the throttle and the engine, and means to heat the fueland air in said channel, said means being heated by the engine coolant,said discharge port and contiguous carburetor parts receiving heat onlyfrom the fuel and air in said channel which have been passed by saidfuel restriction and said air admission port and mixed before beingheated.

2. Means for controlling the ratio of the fuel-air mixture supplied toan internal combustion engine by av carburetor with a throttle by-passcircuit, said by-pass circuit including means for forming a fuel-airemulsion; comprising a heat exchanging element, means for applying heatto said element so that its temperature gradually increases as theengine warms up after starting to a stable maximum value substantiallyindependent of engine speed and load, means for conducting said fuel-airemulsion from said carburetor to said heat exchanging element for thetransfer of heat thereto, and means for conducting said fuel-airemulsion so thermally modified back to said throttle by-pass circuit forforming said fuel air mixture whereby the ratio of fuel to air in saidmixture is changed by the transfer of heat to said emulsion from aricher value suitable for cold engine idling operation to a leaner valuesuitable for warm engine idling operation.

3. Fuel-air ratio controlling means according to claim 2, wherein saidheat exchanging element is connected to the coolant system of saidengine to obtain the heat required for transfer to said fuel-airemulsion.

4. Fuel-air ratio controlling means according to claim 2 furthercharacterized by said throttle by-pass circuit including a conduitby-passing said heat exchanging element, whereby a metered portion ofthe fuel-air emulsion delivered to the engine intake system is subjectedto a change in density by the application of heat thereto.

5. The method of utilizing thermal air expansion and fuelvaporization'to regulate in a gasoline engine'the richness of the chargeaccording to engine temperature where such charge is supplied through acarburetor having an idle by-pass system, comprising the steps ofadjusting the jets and air bleeds in said idle by-pass system to delivera fuel-air mixture sufiiciently rich to operate the engine when cold,conducting said mixture to a heat exchanging device, applying heat tosaid mixture through said device to partially vaporize the fuel andexpand the air therein and thereby reduce the density of said mixture,gradually applying heat to said device so that its temperature increasesas the engine warms up afterstarting to a stable maximum valuesubstantially independent of engine speed and load, and conducting saidmixture so heated to said engine.

6. The method of utilizing thermal air expansion and fuel vaporizationto regulate in a gasoline engine the richness of the charge according toengine temperature, consisting of supplying fuel and air through acarburetor 11mins an idle by'pass System, adjusting the jets and airbleeds in said idle by-pass system to deliver a mixture sufficientlyrich to operate the engine when cold, and applying to a fuel conduit inthe idle by-pass system regulated engine heat to the end that thetemperature of said conduit gradually increases as the engine warms upafter starting to a stable maximum value substantially independent ofengine speed and load, the heat applied to said fuel conduit expandingthe air therein and at least partly vaporizing the fuel therein and thusreducing the fuel delivery of said idle by-pass system to what theengine requires when it is at operating temperature;

References Cited in the file of this'patent

